The ultimate objective of this research is to gain an understanding of the roles of ribonucleic acid and protein synthesis in the regulation of cellular development in simple aquatic fungi. A problem of central interest is the function of the unusual ribosome-containing nuclear cap found in the flagellated zoospores of the non-filamentous organism Blastocladiella emersonii. The formation of the nuclear cap, its function in the zoospore, and the relation of its dispersal to early protein synthesis during germination are being analyzed by the combined techniques of electron microscopy and biochemistry. The function of the nuclear cap, and its relationship to the basic problem of intracellular regulation during differentiation and germination of zoospores, is being studied with plants grown in highly reproducible synchronous cultures. Such cultures are being used to analyze the role of ribonucleic acid and protein synthesis in the formation of specific cellular structures (e.g., discharge papilla, flagella, the nuclear cap, and other organelles) at the molecular level. One area of primary emphasis at present is an analysis of the presence, and in vitro functional capacity, of the components for protein synthesis from the motile but nonsynthetic zoospores. This includes the study of a possible translational control of protein synthesis at the ribosome level. The second primary area of emphasis is a study of the regulation of bulk ribonucleic acid synthesis, and the role of messenger RNA, in specific stages of development.